1. Field of the Invention
This invention relates to a recording apparatus of the kind using a rotary recording medium.
2. Description of the Related Art
The recording apparatuses performing recording on rotary recording media have been arranged in varied manners according to the kind of the recording media to be used and the recording method employed.
These known recording apparatuses include, an electronic still video camera. Unlike the conventional silver halide type camera, the still video camera records a still image on a rotating magnetic disc and is arranged, for example, as shown in FIG. 1 of the accompanying drawings. FIG. 1 is a block diagram showing the operation control system of the still video camera of the above stated kind. The illustration includes an optical system 1 including a photo taking lens; an image sensing circuit 2 which is arranged to photo-electric convert information on an image formed by the optical system 1 and to produce a video signal, the circuit 2 being composed of a CCD or a camera tube, etc.; a signal processing circuit 3 which is arranged to perform a signal processing operation in a prescribed manner on the video signal produced from the image sensing circuit 2 and thus to convert it into a signal form suited for recording on a magnetic disc D; a magnetic head 4; a stepping motor 5 which is arranged to move the magnetic head 4 in the radial direction of the magnetic disc D; a motor driving circuit 6 which is arranged to drive and control the head moving stepping motor 5; the magnetic disc D; a motor 7 which is arranged to rotate the magnetic disc D; a motor control circuit 8 for controlling the motor 7; and a PG detector PG (or a PG coil) which is arranged to detect the rotation phase of the magnetic disc D through a marker member (PG pin), which is disposed in a given position on the magnetic disc D. A synchronizing signal generating circuit 9 is arranged to receive the output signal pg of the PG detector PG and to generate and supply a synchronizing signal to the image sensing circuit 2 and to the signal processing circuit 3 in accordance with the timing of the signal pg. A system controller 10 is arranged to perform control over all the operating circuit blocks and is composed of a CPU. A switch 11 is arranged to close in response to the first step of stroke of a pushing operation performed on a release switch which is not shown but is arranged to give an instruction for a recording action. A switch 12 is arranged to close in response to the second step of stroke of the release switch. Transistors Tr1 to Tr6 are provided for operation control. A reference symbol E denotes a power source battery.
With the apparatus arranged in the above stated manner, a recording operation is performed as follows: The transistor Tr2 becomes conductive when the release switch which is not shown is pushed to the first stroke position thereof. This causes the battery E to effect a power supply to the system controller 10. The system controller 10 then applies a high level signal to the base of the transistor Tr1 to make it conductive. By this, the transistor Tr2 is kept in an on-state. At the same time, the transistor Tr4 is turned on with the base thereof caused to be at a high level. The transistor Tr4 in turn brings the transistor Tr6 into a conductive state. As a result, a power supply is effected to the stepping motor driving circuit 6 and the motor driving system of the motor control circuit 8 respectively. Further, the system controller 10 controls and causes the motor 7 to steadily rotate through the motor control circuit 8. In this instance, the PG detector PG (PG coil) which is disposed on the side of the recording apparatus detects a PG pin p which is provided for phase detection and is disposed in a given position on the disc D as shown in FIG. 2. The PG detector PG (PG coil) then produces one pulse signal as a signal pg every time the disc D makes one turn by detecting the PG pin p. Meanwhile, an FG signal generator which is not shown is arranged to produce a plurality of pulse signals per turn of the disc D. Control for the steady rotation and phase of the disc D are accomplished on the basis of these signals.
Referring to FIG. 2, the PG pin p which is disposed on the side of the disc D is arranged to permit magnetic detection of the rotation phase of the disc D by inducing the lines of magnetic force of a magnet which is disposed on the side of a spindle (not shown). The PG detector PG which is arranged to generate the pulse signal pg by detecting the PG pin p includes a detection coil (PG coil). The detection coil is disposed at a given distance (4.5 mm in the case of a still video camera) away from the rotation shaft of the disc (hereinafter referred to as a spindle) and on a straight line (hereinafter referred to as an in-line) L which represents the locus of the radial movement of the head 4 taking place as the disc is driven. The rotation phase of the disc is thus detectable.
When the release switch is further pushed to the second step position thereof, the system controller 10 turns the transistor Tr5 on through the transistor Tr3. As a result, the power supply is effected to the image sensing circuit 2 which includes a solid-state image sensor such as a CCD, the synchronizing signal generating circuit 9 and the signal processing circuit 3. Then, timing signals of varied kinds necessary for forming a video signal to be recorded on the disc D, such as a color synchronizing signal C-SYNC, a vertical synchronizing signal V-SYNC, a color blanking signal C-BLANK, etc., are generated. After a clearing action on the CCD, an exposure is effected by opening and closing a shutter to accomplish a photo taking operation.
With the power supply effected to the image sensing circuit 2, the synchronizing signal generating circuit 9 and the signal processing circuit 3, actual recording on the disc D is performed after the lapse of a given length of time required before these circuits become stably operable. In other words, after the lapse or a given period of n sec or, for example, 7H.+-.2H (H: a horizontal scanning period), the vertical synchronizing signal is recorded on the disc D. Following this, video signals are recorded. The signal recording position on the disc is determined in accordance with a common format to ensure the interchangeability of apparatuses.
In accordance with the above stated arrangement of the apparatus, however, electric energy is wastefully consumed before actual recording on the disc, because: After the power supply is effected to an image sensing system including the image sensing circuit 2, the signal processing circuit 3 and the synchronizing signal generating circuit 9, all these circuits become operative. The power supply to the signal processing circuit 3 is not required until reading image information from the image sensor such as CCD or the like after completion of an exposure. However, in the case of a circuit of an analog system, it is generally necessary to switch the power supply on well in advance of the use of it as the circuit operation is often unstable immediately after the power supply is switched on. Assuming that the power supply is switched on at the timing of a PG pulse signal, at least about one field period (16.7 m sec) has been necessary before the stabilization of the circuit.
Therefore, an attempt to start recording at a recording start position on the disc after the lapse of a given period (7H.+-.2H) from a point of time at which the PG pulse signal is detected would result in an inadequate record as the circuit has not been stabilized as yet, particularly in the case of an analog system circuit which has a long rise time. It is thus impossible to immediately begin to record from the recording start point which comes after the lapse of the period of 7H with the release button pushed to the second step position of its stroke. In view of this, therefore, it is necessary to wait for another field period and to begin recording on the disc after the lapse of another period of 7H following a PG pulse signal obtained after one turn of the disc.
In other words, the apparatus necessitates a long waiting period of time before actual recording after the power supply is effected to each circuit. This not only wastes the electric energy but also hinders photographing at a higher speed and is detrimental particularly to a high speed continuous photographing operation. The electric energy consumption and the hindrance to a higher speed has presented a serious problem for a still video camera or a like apparatus using a battery.